The Sigtest is usually used as a command line tool executed in their one dedicated JVM. In JCK, there are some cases where the sigtest is executed programmaticly in the single JVM shared by tests. In particular, JCK-compiler and JCK-devtools test suites contain thousands of small separate tests, each of them runs the sigtest against own signature data file, preliminary generated on RI (JDK). So it would be good to see, if there is something in the sigtest that may be optimized to improve the performance of running sigtest in the same JVM in both static and reflection modes.
One of concrete thing, I could imagine, would be providing a standard Ant task served for signature generation.